Siemens SIMATIC ET 200SP Manual page 34

Applications of the F-I/O module
5.4 Application: Connection of a fail-safe digital input to each digital output
If there is cross-circuit to another output at a non-passivated, switched off output, a brief
1-signal can occur with a duration of 2x max. cycle time (T
test (T
If there is a cross-circuit between two outputs, the test pulses of light tests of the respective
other output are also visible. With a different setting of the "Max. readback time light test"
parameter, this can cause cyclically occurring 1-signals that last as long as the longest
configured "Max. readback time light test".
If the above mentioned 1-signals dangerously affect the plant when a cross-circuit occurs
between outputs, you need to guard against the cross-circuits between the outputs with a
cross-circuit-proof installation, for example, with separate sheathed cables or separate
cable ducts.
34
WARNING
).
rb
Digital output module F-DQ 8x24VDC/0.5A PP HF (6ES7136-6DC00-0CA0)
) + Max. readback time dark
cycle
Manual, 05/2017, A5E38578424-AA